Pollution of Water Resources from Agricultural Fields and Its Control - Practices of Irrigation and On-farm Water Management - page 242

7.7.2 Nitrogen Management ......................... 265
7.7.3 Cultural Management/Other Forms
of Management ............................ 266
7.8 Models in Estimating Solute Transport from Agricultural and Other Sources .... 266
Relevant Journals ................................ 267
Questions .................................... 267
References ................................... 269
Chemicals from agricultural field and other sources frequently enter the soil, sub-
soil, and aquifer. This may happen either by normal management practices or by
accident, and the resulting chemical residues pose hazards to the environment and
ecosystem. Whether we are using fertilizer or other pollutants, it is useful to know
how fast it moves.
Surface and groundwater pollution caused by chemicals from agricultural (e.g.,
fertilizers, pesticides, insecticides, herbicides) and industrial sources have caused
public concern for decades. Chemicals migrating from municipal disposal sites also
represent environmental hazards. The same is true for radionuclides emanating from
energy waste disposal facilities. Extensively and, specifically, intensively cropped
areas are major sources of groundwater recharge. Excessive use of chemical fertiliz-
ers can lead to pollution of surface and groundwater if associated with high rainfall
or irrigation, shallow rooted crops, and sandy soils. To preserve the groundwater
and reduce economic losses for the farmers, estimation of solute/chemical leaching
below the root zone and prevention of such leaching is crucial.
7.1 Pollution Sources
To check or mitigate the adverse effects of pollution, it is necessary to understand
the sources, the characteristics, and the interaction processes of the pollutants with
the environment.
The sources of pollution can be broadly divided into two classes:
(i) Point source
(ii) Nonpoint source (or diffuse source)
7.1.1 Point Sources
Point source of pollution is a type of pollution that can be traced to a single
source, such as pipes, wells or ditches, industrial or metropolitan outlet, and sewage
treatment plants. It has a clearly definable point of entry into the waterways.
7.1.2 Nonpoint Sources
Nonpoint source (also termed diffuse source) is the source that cannot be traced to a
single point but rather distributed throughout the system. Diffuse pollution loads are